More than 550 million years ago, a small, flattened animal moved across the seafloor and repeatedly favored one direction. Fossils of Spriggina floundersi suggest that when it bent its body, it tended to turn right.

That preference may represent the oldest-known example of lateralized behavior, in which an animal consistently favors one side of its body over the other. The evidence pushes the roots of this behavior back to the Ediacaran Period, long before the emergence of most familiar animal groups.

The study, published in Scientific Reports, was led by researchers at the American Museum of Natural History, Florida State University, Harvard University, and the University of California, Riverside. By examining how Spriggina fossils were curved, the researchers found a population-wide pattern rather than a random mix of leftward and rightward movement.

“When we talk about being right-or-left-handed, most people likely think about how they hold a pencil or kick a soccer ball. But our research shows that an animal without hands or feet, living over 500 million years ago, may have had its own version of handedness,” said lead author Scott Evans, assistant curator of invertebrate paleontology at the museum.